A computer network links together two or more computers by a communication pathway or paths, allowing the computers to share resources and information. Networks are fast becoming a standard feature of the modern workplace. Local-area networks of personal computers and workstations are practically a necessity in large offices where many individuals must share and exchange computerized information on a daily basis. Wide-area networks connect users and computers at distant locations across the country and around the world.
In a network, a sever computer is one that provides a resource to a client computer. The same computer can be client in one context and server in another. For example, suppose that computer A has a large hard disk for storing files for an entire office, but lacks its own printer. Elsewhere on the office network, computer B has a printer but no hard disk. If a user of computer B wishes to access a file stored remotely on the disk of computer A, then computer B is the client and computer A is the (file) server. If a user of computer A wishes to print a locally stored file using the printer of computer B, then computer A becomes the client and computer B is the (print) server. A computer that can act as both client and server according to the context is called a peer server.
Resource sharing implies issues of resource security. In general, the user of a client computer cannot be trusted with unlimited access to all server resources. Accordingly, the user is required to supply a password in order to log onto the network. Additional mechanisms are used to limit access to particular resources. One such mechanism is a simple share/no-share switch, which can be set either to allow remote access to a given resource from client computers or to restrict remote access so that the resource can be accessed only locally from the server computer. More sophisticated mechanisms used to limit access to particular resources include access control lists, which specify the privileges of particular users with respect to particular resources or collections of resources.
Unfortunately, known operating systems for networking personal computers and workstations, such as Microsoft.RTM. Window.TM. NT by Microsoft Corp. (Redmond, Wash.), employ resource security models that are complex and difficult for users, especially new users, to understand. Compounding the difficulty are highly nonintuitive user interfaces that frustrate users' attempts to understand the security models and to manipulate resource protections within the models, for example, to manipulate user access permissions for file folders or directories stored in a persistent information store such as a hard disk.